1. Field of the Invention
This invention relates to a magnetic bubble recording element, and more particularly relates to a magnetic bubble recording element in which magnetic bubbles are optically written and read.
2. Description of the Prior Art
Magnetic bubble recording elements have been developed in parallel with semiconductor recording elements. They have the features of being non-volatile memories and being stable in their operation even at high temperatures, and hence their applications for memories are being developed.
An exemplified form of a conventional magnetic bubble recording element is shown in FIGS. 1A and 1B. FIG. 1A is a cross-sectional view thereof, and FIG. 1B is a plan view thereof.
In FIGS. 1A and 1B, there are shown a garnet substrate 1 in which magnetic bubbles are formed, a soft magnetic layer 2 consisting of permalloy or the like for transferring magnetic bubbles, a spacer layer 3 for insulation and a conductive film (interconnection patterns or the like) 4 for generating magnetic field for transferring bubbles or for transmitting several kinds of signals when information is recorded and reproduced.
In order to transfer magnetic bubbles in conventional recording elements, the soft magnetic layer 2 is, for example, magnetized by a rotating magnetic field in a facial direction (i.e., a direction parallel to the upper surface of the substrate 1) which is generated by a coil provided outside the magnetic bubble recording element, or by supplying current in the conductive film 4 shown in FIG. 1B, or the like. On this occasion, in FIG. 1A, magnetic bubbles held in the garnet substrate 1 are drawn and transferred by a bubble capturing point (a generating point of magnetization) which generates around the circumference of the pattern of the soft magnetic layer 2 and moves.
Magnetic bubbles are formed, for example, by applying to the garnet substrate 1 a local vertical magnetic field which is generated by providing a current to the conductive film 4 near a specific point in the pattern of the soft magnetic layer 2. Magnetic bubbles are detected by detectors (magnetic sensors), such as Hall elements, which are disposed in intermediate locations in the pattern of the soft magnetic layer 2.
In such a conventional magnetic bubble element, however, it is necessary to perform fine processing for providing interconnection patterns of signal lines for writing or reading on a wafer, and for the mounting of a magnet, a coil or the like for generating the biasing magnetic field, and it is difficult to provide a low-cost, small and light-weight recording element.
In order to solve such problems, the assignee of the present invention has proposed, in U.S. Pat. application Ser. No. 434,538 filed on Nov. 8, 1989, which is a continuation of application Ser. No. 125,824 filed on Nov. 23, 1987, now abandoned, which is a continuation of application Ser. No. 801,401 now abandoned, and application Ser. No. 593,252 filed on Oct. 1, 1990, which is a continuation of application Ser. No. 257,130 filed on Oct. 7, 1988, now abandoned, which is a continuation of Ser. No. 883,921, now abandoned, a method for optically writing magnetic bubbles and a method for optically reading magnetic bubbles (the contents of both applications are incorporated herein by reference). By using these methods, patterning for writing or reading on a wafer can be made simple.